1. Field of the Invention
The present invention relates to communication networks and, more particularly, to a method and apparatus for supporting multiple simultaneous wireless connections in a wireless local area network.
2. Description of the Related Art
Data communication networks may include various computers, servers, nodes, routers, switches, bridges, hubs, proxies, and other network devices coupled to and configured to pass data to one another. These devices will be referred to herein as “network elements.” Data is communicated through the data communication network by passing protocol data units, such as Internet Protocol packets, Ethernet Frames, data cells, segments, or other logical associations of bits/bytes of data, between the network elements by utilizing one or more communication links between the devices. A particular protocol data unit may be handled by multiple network elements and cross multiple communication links as it travels between its source and its destination over the network.
In a typical wireless network, wireless access points provide wireless access to wireless clients. Wireless networks rely on the propagation of wireless signals which may be affected by numerous environmental factors. For example, changing environmental conditions and the activities of adjacent wireless access points can affect the reach of the signal and the bandwidth available over a channel on the wireless signal. Especially in ad-hoc networks, where the placement of wireless access points is not extensively planned and may not be extensively centrally managed, and where the wireless access points themselves might be mobile, the signal characteristics may vary considerably from place to place and temporally within the same place.
Conventionally, wireless standards generally require a wireless client to be associated with no more than one wireless access point. Thus, a wireless client will associate with a given wireless access point and communicate through that wireless access point until signal characteristics deteriorate to the point where the wireless client is required to search for a new access point on the network. The wireless client will then scan the signal channels to find the next available wireless access point and make a new association with the selected wireless access point.
For example, when a wireless client is required to handoff to another primary wireless access point, the wireless client may scan a beacon (output by the wireless access points) to find an adjacent wireless access point that has a relatively strong signal. Any number of methods may be used to select an available wireless access point. The wireless LAN client will then try to send an association request and authentication request towards the new primary wireless access point. Upon receipt of a reply from the new wireless access point that the association and authentication has been accepted, the wireless LAN client will initiate a Request To Send (RTS) message to the new associated wireless access point. Once the wireless access point has the capacity to allocate bandwidth to this specific request, a Clear To Send (CTS) message is sent back to the requesting wireless client indicating that the wireless client is clear to start communicating through the wireless access point.
Unfortunately, the handoff process may take up to or in excess of 100 ms which, for real time applications such as audio and video transmissions and certain other data applications, may exceed acceptable limits. Accordingly, it would be advantageous to provide a faster mechanism for facilitating hand-offs in a wireless local area network.